In order to avoid purchasing a specialized, dedicated tea brewing machine, many consumers and institutions have attempted to utilize their automatic drip coffee machines to brew tea. It is estimated that nearly 25% of all iced tea served in restaurants and away from home is brewed with automatic drip coffee machines.
A typical coffee brew machine comprises a base member with a heater element used to support a glass coffee pot and a coffee filter holder attached to the base in the position above the coffee pot. The coffee filter holder is typically frusto-conical in shape with one or more central apertures through the bottom wall and is designed to receive a disposable coffee filter. Many such holders also contain a wire basket or ribbed inner surface within the filter holder to prevent the filter from pressing against the solid outer wall of the filter holder. This prevents the moistened filter from forming a liquid impervious seal with the solid outer wall, and ensures that the entire surface of the filter is available for filtering purposes.
The coffee filter is normally fabricated from porous paper and is also frusto-conical in shape so as to be received within the coffee filter holder. In use, the coffee filter will be placed in the coffee filter holder and a measured amount of roast and ground coffee is placed in the bottom portion of the coffee filter. A measured quantity of hot water is then directed into the interior of the coffee filter onto the ground coffee. As the water passes through, the coffee expands and floats up in the filter increasing the coffee/water contact area. The water will then percolate through the ground coffee and flow through the bottom and lower side portions of the porous coffee filter and through the coffee filter holder apertures down into the coffee pot.
One disadvantage with attempting to use the aforementioned system for brewing tea is that the tea leaves must be individually measured into a filter (usually a coffee filter) each time a pot of tea is to be brewed. This is time consuming and may result in too much or too little tea being placed in the filter. If the amount of tea placed in the filter varies to any significant extent, then the brew strength of the resultant tea will also vary. Another disadvantage is that separate receptacles must be provided for the individual filters and the tea leaves. Lastly, when measuring the tea leaves into the filter or disposing of a used filter, the spent tea leaves are often spilled onto the counter area or the floor resulting in waste of tea leaves and a waste of time in cleaning up.
Coffee manufacturers have substantially eliminated the pot-to-pot brew strength inconsistencies arising from poor measurement of coffee by the operator by providing unitized pouches, each containing a predetermined volume of roast and ground coffee suitable for brewing a single pot of coffee of reasonably consistent strength from one pot to the next. However, these unitized pouches add to cost and disposal problems due to the need for additional packaging equipment and material. In addition, they do not eliminate the messiness problems normally associated with bulk coffee/paper filter systems, since loose grounds and filters must still be disposed of. Corresponding unitized tea pouches have been developed by tea manufacturers, but these fare no better than the coffee pouches in addressing these drawbacks.
Recently, coffee filter packs have been designed in an attempt to overcome some disadvantages from this method. Most of these coffee filter packs are made with heat sealable filter paper or from non-woven polyester, polypropylene, polyethylene or a combination thereof. These materials are typically more expensive than conventional filter paper, which is typically comprised almost entirely of wood fiber. Moreover, these filter packs are usually circular or square in shape and simply cover the bottom wall of the coffee filter holder. These filter packs are often improperly positioned in the coffee filter holder resulting in inconsistent brew strength from pot-to-pot, since their shape and materials of construction allow water to escape around the sides and through the coffee filter pack without sufficient exposure to all of the coffee contacted in the brew chamber of the filter pack. This results in poor coffee extraction. Furthermore, the coffee will often migrate to one side of the filter pack so that much of the water which does pass through the brew chamber of the filter pack does not contact any coffee. As a result, these filter packs produce brewed coffee with a relatively low level of extracted flavor solids as well as an inconsistent brew strength from pot-to-pot.
Experience to date has been that filter packs of the prior art do much to overcome the messiness of the bulk coffee/filter paper systems they have replaced. Unfortunately, they have typically exhibited lower extraction efficiencies than the bulk coffee/filter paper systems. In addition they have typically introduced much worse pot-to-pot brew strength variation than bulk coffee systems using premeasured unitized pouches of roast and ground coffee in conjunction with paper filters.
Once again, tea manufacturers have developed corresponding filter packs for their products. Unfortunately, these tea filter packs incorporate the same problems which plague the coffee filter packs, and also additional problems which arise due to the differences in brewing characteristics between coffee and tea.
In general, tea leaves absorb water and expand to a much greater extent than roast and ground coffee. Because of this degree of expansion, tea filter packs which allow no more room for expansion than typical coffee filter packs may in fact rupture if the expanded volume of the tea leaves is greater than the maximum available volume within the tea filter pack. This results in pieces of tea leaves floating loosely in the brewed tea, and likely passing down through the filter holder and into the finished product, an undesirable occurrence.
Ground coffee also generally contains a much greater proportion of fine, dust-like particulate material than tea leaves which have been crushed or shredded. When wet, coffee tends to pack more tightly and presents a much greater obstacle to the passage of water than does a similar quantity of tea leaves. Wet coffee particles also exhibit a much greater tendancy to clog the pores of porous filters than tea leaves. This clogging tendancy is in large part the reason coffee brewing machines incorporate a wire basket or ribbed inner surface inside the filter holder, i.e., to maximize the available filtering area. Tea filter packs thus relying on the flow rate of the coffee maker to control brewing time will not permit the tea to steep in the hot water for a sufficient amount of time for good extraction, as water will tend to pass too rapidly downwardly through the entire lower surface of the tea filter pack and out through the bottom of the filter holder. This results in poor extraction efficiency and poor utilization of the tea leaves.
By way of contrast, Applicants have learned that in order to minimize brew time, maximize flavor solids extraction and make a good pot of tea, a substantial portion of the hot water directed into the filter pack must contact the tea in the brew chamber after a substantially steady state brewing condition has been established within the brew chamber, i.e., after the brew chamber has been completely flooded with the incoming hot water so that the chamber expands to its maximum volume and allows substantially all of the tea leaves contained therein to loosely float within the chamber.
Applicants have further learned that this is preferably done by providing a substantially water impermeable side wall having a height which is sufficient to retain at least enough water to permit complete immersion of the brew chamber when the brew chamber is in its fully expanded condition in combination with inlet and discharge flow rates into and out of the brew chamber that will cause the water to build up and puddle the tea inside the brew chamber. If the water is not allowed to build up inside the brew chamber (as is typically the case with prior art filter packs) or if the tea leaves contained in the brew chamber of a prior art filter pack have shifted to one side of the brew chamber when the prior art filter pack is placed in the filter holder, the failure to properly control the inlet and outlet flow rates and the failure to provide a substantially water impermeable side wall having a height which is sufficient to retain at least enough water to completely immerse the brew chamber when the brew chamber is in its fully expanded condition will allow much of the water to flow directly through or around the brew chamber of the prior art filter pack without ever contacting any of the tea leaves therein.
In addition, Applicants have learned that the brew chamber must be large enough to allow the tea leaves enough room to expand and float while water is building up in the brew chamber in order to achieve sufficient tea/water contact, i.e., to achieve a steady state brewing condition. This helps to prevent channeling of the water through the filter pack without sufficient tea/water contact. Minimizing channeling is important, since channeling of the hot water directly through the brew chamber without sufficient tea contact results in poor and inconsistent tea flavor solids extraction.
It is therefore an object of the present invention to provide an improved tea filter pack which overcomes many of the problems associated with the prior art brewing systems which employ bulk tea leaves and discrete paper filters, which approximates the extraction efficiency of systems employing bulk tea leaves and discrete paper filters, which provides reasonably consistent pot-to-pot brew strength without the need for premeasured unitized pouches of tea leaves, and which avoids the pot-to-pot brew strength inconsistency typically associated with prior art filter packs.
It is another object of the present invention to provide such an improved tea filter pack which is relatively insensitive to operator placement within the filter holder of the coffee machine, which includes a substantially impermeable vertically oriented, conformable side wall, which is made almost entirely of relatively inexpensive flexible material, such as ordinary filter paper, and which can be used with a wide range of existing coffee filter holders without any need to modify them.